Hydrocarbon oil and fuel oil compositions typically include additives to enhance performance. For example, such oils typically comprise a mixture of at least one hydrocarbon base oil and one or more additives, e.g., dispersant, viscosity modifier, wax crystal modifier (e.g., pour point depressant), detergent, antioxidant, etc. additives, where each additive is employed for the purpose of improving the performance and properties of the base oil in its intended application; e.g., as a lubricating oil, heating oil, diesel oil, middle distillate fuel oil, power transmission fluid and so forth.
Dispersants are typically polymeric materials with an oleophilic characteristic providing oil solubility and a polar characteristic providing dispersancy. The number average molecular weight of a polymer "backbone" used as a vehicle for synthesizing a dispersant is generally 10,000 or less.
Viscosity modifiers also are typically polymeric materials that can be used neat or with suitable functionalization and/or derivatization be used as multifunctional viscosity modifiers. When used as viscosity modifiers the polymer or copolymer backbone generally has a number average molecular weight of greater than about 15,000.
Dispersants used in lubricating oils typically are hydrocarbon polymers or copolymers modified to contain nitrogen- and ester-based groups. Polyisobutylene is commonly used in the preparation of dispersants, although other hydrocarbon polymers, such as ethylene-.alpha.-olefin copolymers, can be employed as well. It is the primary function of a dispersants to maintain in suspension in the oil those insoluble materials formed by oxidation, etc. during use, thereby preventing sludge flocculation and precipitation. The amount of dispersant employed is dictated by the effectiveness of the particular material in achieving its dispersant function. Dispersants can have additional functions, such as viscosity modifying properties and antioxidancy, depending on their chemical and structural characteristics.
Nitrogen- and ester-based dispersants can be prepared by first functionalizing a long-chain hydrocarbon polymer, e.g., polyisobutylene, and ethylene .alpha.-olefin (EAO) copolymers with maleic anhydride to form the corresponding polymer substituted with succinic anhydride groups, and then derivatizing the succinic anhydride-substituted polymer with an amine or an alcohol or the like. Polyisobutylene generally contains residual unsaturation in amounts of about one ethylenic double bond per polymer chain, positioned along the chain, whereas the more recently developed EAO copolymers (based on metallocene catalyst systems) contain a substantial amount of terminal vinylidene unsaturation (see, e.g., WO 94/19436, published Sep. 1, 1994, incorporated herein for the purposes of U.S. patent prosecution.) The ethylenic double bonds serve as sites for functionalization by, for example, the thermal "ene" reaction (i.e., by direct reaction with maleic anhydride or one or more other dicarboxylic acid moieties).
Polyisobutylene (PIB) polymers employed in conventional dispersants are sometimes limited by viscosity effects associated with the polymer as well as limited reactivity. EAO copolymers offer improvements, since these products are primarily terminated with vinylidene type unsaturation, but there are additional efficiencies which can be realized with further improvements in reactivity for functionalization and derivatization; also such copolymers require the use of multiple monomer feed steams to produce a copolymer.
The use of highly diluted, purified refinery monomer feedstreams for ethylene and .alpha.-olefin polymerization using a metallocene catalyst system to produce an ethylene .alpha.-olefin copolymer has been disclosed in U.S. Ser. No. 992,690 (filed Dec. 17, 1992), incorporated herein for the purposes of U.S. patent prosecution. As a consequence of using a Ziegler-Natta catalyst generally, or a metallocene based catalyst system specifically, there are necessary concerns about the purity of the feedstreams since such catalyst systems are particularly sensitive to moisture as well as nitrogen, sulfur and oxygen compounds which can deactivate the catalyst (see, e.g., WO93/24539, page 13, published Dec. 9, 1993).
Johnson, L. K. et al., in J. Am Chem Soc., 1995, 117, 6414, describe the use of Ni and Pd complexes using various activators (including MAO and alkyl aluminum chloride) for the solution homopolymerization of ethylene, propylene, and 1-hexene. Polymers varying in molecular weight, branch length and crystallinity are disclosed.
Johnson, L. K. et al., in J. Am Chem Soc., 1996, 118, 267, describe the solution copolymerization of ethylene with acrylate comonomers, including methyl acrylate, tert-butyl acrylate, perfluorinated octyl acrylate, and methyl vinyl ketone and propylene with methyl acrylate and perfluorinated octyl acrylate, using a Pd catalyst. The copolymers are disclosed as random, amorphous, and branched (it is stated the ethylene copolymers have approximately 100 branches/1000 C atoms) with functional groups located predominantly at branch ends.
Brookhart, M. S. et al., in published patent application EP 0 454 231 A2 (1991) describe a catalyst for the polymerization of ethylene, .alpha.-olefins, diolefins, functionalized olefins, and alkynes. The general description of the catalyst broadly includes Group VIIIb metals (Groups 8, 9, 10); cobalt and nickel are exemplified in solution polymerizations to produce oligomers and polymers of limited molecular weight.
Brookhart, M. et al. in J. Am. Chem. Soc., 1994, 116, 3641 and 1992, 114, 5894 describe the use of Pd(II) catalysts to produce alternating olefin/CO copolymers. (Subsequently, it is noted in J. Am Chem Soc., 1995, 117, 6414 that the complexes used in the 1992 reference only dimerize ethylene.)
Keim, W. et al. in Angew. Chem., Int. Ed. Engl., 1981, 20, 116 describe the use of an aminobis(imino)phosphorane complex of Ni to polymerize ethylene under pressure in a toluene solution. The polymer is said to contain short chain branches.
Mohring, V. M. et al. in Angew. Chem., Int. Ed. Engl., 1985, 24, 1001 describe the use of the catalyst system aminobis(imino)phosphorane complex of Ni to polymerize C.sub.3 to C.sub.20 linear .alpha.-olefins and singly branched .alpha.-olefins. Olefins containing quaternary carbons, vinylene, or vinylidene groups did polymerize, but copolymers of .alpha.-olefins could be obtained. Polymerization of linear .alpha.-olefins produced polymers containing methyl branches evenly spaced corresponding to the length of the olefin chain. (A "chain running" mechanism proposed as an explanation for the branched polymer structure is also described by L. K. Johnson in J. Am Chem Soc., 1995, 117, 6414, above.)
Peuckert, M. et al. in Organometallics, 1983, 2, 594 describe a Ni catalyst for the oligomerization of ethylene in toluene. The catalysts are said to contain the chelating phosphino-acetate ligand used in SHOP catalysts. The C.sub.4 to C.sub.24 oligomers are &gt;99% linear and &gt;93% .alpha.-olefin. An ethylene/hexene co-oligomerization produced product with no detectable branches.
A component described as useful in lubricating oil flow improvers described in U.S. Pat. No. 4,839,074 includes polymers and interpolymers of side chain unsaturated monoesters which are unsaturated esters, generally acrylate or 2-alkylacrylate monoesters represented by a defined formula.
It has been found in the present invention, that further improvements can be achieved in the performance of fuel and lubricant additives, particularly including ashless dispersants and wax crystal modifiers, based on the use of copolymers derived from polar and olefinic monomers; also, significant improvements in the economics of producing and using such additives can be achieved by selective use of late-transition-metal catalysts and polymerization processes which use highly dilute refinery or steam cracker olefin feedstreams to produce a copolymer having a unique combination of properties for subsequent functionalization and derivatization.